diff --git a/cartographer/common/histogram.h b/cartographer/common/histogram.h
index 4b49141..aa41141 100644
--- a/cartographer/common/histogram.h
+++ b/cartographer/common/histogram.h
@@ -17,7 +17,6 @@
 #ifndef CARTOGRAPHER_COMMON_HISTOGRAM_H_
 #define CARTOGRAPHER_COMMON_HISTOGRAM_H_
 
-#include <map>
 #include <string>
 #include <vector>